UNS: Collaborative Research: Biodiesel-derived butanol: Lipid vesicle mediated extraction enables continuous fermentation processes

University Of Rhode Island, Kingston RI

Investigators

Abstract

PI: Geoffrey D. Bothun / Carmen Scholz Proposal Number: 1508844 / 1509244 Butanol is a promising advanced biofuel because it has a high energy content approaching that of gasoline, and can serve as a drop-in replacement fuel. However, butanol is more difficult to produce by fermentation relative to ethanol. This is because the butanol product is toxic to the fermentation process, resulting in low concentrations of butanol that are too costly to recover economically. This project will develop a novel fermentation process that uses a nontoxic solvent to remove butanol while it is being produced, which reduces toxicity and increases overall butanol yield. Furthermore, the microorganism chosen for study, Clostridium pasteurianum, makes butanol from fermentation of crude glycerol, the by-product of biodiesel manufacture. Through this investigation, undergraduate and graduate students will be trained in renewable fuel technologies, and will receive specialized training in communication skills and public outreach. The production of butanol by fermentation typically results in low butanol yields due a variety of factors, including low butanol tolerance of microorganisms, difficulty in redirecting the metabolic pathway towards butanol biosynthesis, and limitations of conventional extractive fermentation techniques. Recently, ongoing research has shown that the bacterium Clostridium pasteurianum can achieve high butanol yields using crude glycerol as the sole substrate. Crude glycerol is the byproduct of biodiesel production from fatty acid feedstocks. The overall goal of this research is to enhance butanol production by C. pasteurianum through understanding of the relationships between butanol tolerance and its extractive removal by biocompatible lipid vesicles during continuous fermentation on crude glycerol as the substrate. Continuous cultures will be used to determine changes in membrane lipid composition and maintenance energy in response to butanol and substrate addition. This approach will used to connect tolerance, toxicity, and substrate utilization to butanol production. Continuous culture combined with lipid vesicle-based extractive fermentation has the potential to enhance the butanol yield through two processes. First, vesicle-mediated extraction of the crude glycerol will be studied to remove residual fatty acids in the biodiesel-derived glycerol, which are known to inhibit glycerol fermentation to butanol. Second, in situ extractive fermentation with the biocompatible lipid vesicles will be studied for its potential to stimulate the metabolic pathway associated with butanol biosynthesis through the mass-action effect. The project also provides opportunities to educate students, teachers, and communities about the sustainable production of biofuels, and to develop the communication skills of students in this context through Metcalf Institute at the University of Rhode Island. Interdisciplinary modules will be created where students from the University of Rhode Island and the University of Alabama in Huntsville will work together on bioseparation processes relevant to biorefinery operations.